I. Field of the Invention
The present invention relates generally to the field of power distribution, and more particularly to a power distributor adapted to minimize peak power demand.
II. Description of the Related Art
There has been a trend towards greater use of electrical power not only in residence but also in commercial applications. Typically, in businesses, there are multiple users of large amounts of electrical power to operate various systems, and this creates an extremely large demand for power when two or more such systems are operated concurrently.
When there is a large demand for power, the company supplying the power must have sufficient power available to meet the maximum expected demand. This demand and expectation requires the company supplying the power to have the capacity to generate the power and meet the demand. Inefficiencies result because, typically, the electric generating company builds plant facilities that, for the majority of time, can very well exceed the electrical demand. Conversely, there are periods for several hours during a 24 hour period in which there is relatively little demand followed by relatively short periods in which there is exceptionally high demand. As a result, the large capacity of a power generating company is virtually wasted for long periods of time and is called into use for only short periods. Consequently, there is an excessive capital expenditure on the part of the electric generating company to be able to supply peak demand for electrical power.
There have been efforts to resolve the problem of peak demand for electrical power by the relatively simple solution of penalizing a user of electric power by increasing the charge for electrical power in accordance with the power demand, While such a system produces revenue with which the power company can provide the power to the system, it does nothing to prevent the building of overcapacity by the power company. Further, because of existing regulatory systems, power companies typically have little interest in reducing the level of power usage because the regulatory authorities allow the power companies to charge the ultimate end use for the cost of plant facilities to generate the expected demand of power. With the lack of incentive upon the power generating company to reduce the power demand, it falls upon the ultimate end user to do whatever that user can do to reduce the power utilized by the user. Systems have been devised wherein one monitors the total power used and selectively disconnects certain electrical loads on a priority basis when the demand reaches a predetermined level. When the demand decreases, various systems have been utilized for reconnecting loads on accordance with the priority of the loads. These prior art systems have taken the form of very complex systems, generally including some form of electronic data processing means for storing information, monitoring power use and making decisions based upon the stored information. Such systems are necessarily expensive and tend to be useable only in large groups of users or where large groups of power systems are utilized. For instance, in U.S. Pat. No. 4,066,913 to Manning et al, an electric load distributor is disclosed which operates by having a higher priority load disabling other loads having lower priority through the use of timers, thermostats, coils and switches on a somewhat mechanical basis. In U.S. Pat. No. 4,163,271 to Sturrock, an electric load distributor overcomes the difficulties of the prior art by providing a switching means which comprises a current sensing means for determining when a current is present and having switch means operable by the current sensing means to cancel loads at specific current-draw limits.
In accordance with the present invention and the contemplated problems which have and continue to exist in this field, the invention features a load distributor adapted to distribute the various electrical loads of a single power user.
In one aspect, the invention features a power distributor, including a current sensor having a load input and a sensor output, a control unit connected to the current sensor, the control unit including, a current sensor input connected to the sensor output, at least one control output adapted to respond to a current in the current sensor, a control switch connected to each of the at least one control output and a micro-controller having a memory, the micro-controller electrically coupled to the current sensor input and the at least one control output.
In one implementation, the micro-controller includes a timer and a timer switch.
In another implementation, the memory includes a non-timer process and a timer process, wherein the non-timer process comprises instructions to distribute power to the at least one output when a current in the current sensor exceeds a first threshold and cut power to the at least one output when the current in the current sensor drops below a second threshold and wherein the timer process comprises instructions to distribute power to the at least one output when a current in the current sensor exceeds a threshold for a first time interval and cut power to the at least one output if the current remains in excess of the threshold for a second time interval.
In another implementation, the current sensor is a current transformer.
In still another implementation, the current sensor includes an input adapted to receive a plurality of conductors, each of the plurality of conductors having a unique current level.
In yet another implementation, the timer is based on a line frequency.
In another aspect, the invention features a method of controlling power in a power distribution system, including providing a first load having a first current having a plurality of threshold values, providing a second load having a second current, monitoring the threshold values of the first current and based on the threshold values of the first current, selectively cutting off and redistributing the second current to the second load.
In an implementation, selectively cutting off and redistributing the second current includes distributing the second current to the second load when the first current exceeds a first threshold value and cutting the second current to the second load when the first current drops below a second threshold value.
In another implementation, the plurality of threshold values vary with time and selectively cutting off and redistributing the second current includes distributing the second current to the second load when the first current exceeds a threshold value for a first time interval and cutting the second current to the second load if the current remains in excess of the threshold value for a second time interval.
In another implementation, the method includes providing at least one additional load having an additional current and based on at least one of the threshold values of the first current and the second current, selectively cutting off and redistributing the additional current to the at least one additional load.
In still another aspect, the invention features an electric distribution system, including a plurality of circuits, each having a plurality of loads and a peak load distributor, including a current sensor having a load input and a sensor output; and a control unit electrically coupled to the current sensor.
In an implementation, the electric distribution system further includes a remote meter and communications module connected to the peak load distributor.
One advantage of the apparatus is that is provides a single microprocessor chip to execute control algorithms based on current amplitude and time to open and close output contacts to various priority loads. The output contacts are generally put in series with the power applied to a load to disable the load to lower the peak demand.
Another advantage is that the timing portion of the controller algorithm allows the controlled load to operate part of the time during peak demand periods.
A further advantage is that the system monitors electric loads wherein the completion or interruption of a circuit is determined by the level of current present or absent in a monitored load at different times of the day or night.
Other objects, advantages and capabilities of the invention will become apparent from the following description taken in conjunction with the accompanying drawings showing the preferred embodiment of the invention.